The goal of our research effort is to define the role of the unique cell membrane glycoproteins called glycophorins in control of cell growth and cell division. To date we have demonstrated that these molecules are associated with structural intramembrane particles in the cell membrane and that the density and distribution of these membrane constitutents dramatically change in response to cell-to-cell contact and following antigen-cell interaction. The experiments to be performed in the future will focus on the biochemical, biophysical and ultrastructural significance of these changes related to the neoplasic transformation.